Sagittal T1-weighted MR image (a) shows a hazy appearance of the subarachnoid space (yellow arrow) in the distal thecal sac. Fluid layers dependently in the thecal sac from blood products and/or proteinaceous debris (red arrows). Sagittal enhanced T1-weighted MR image (b) with fat-saturation shows diffuse enhancement of the CSF as well as thick sheet-like enhancement of the cauda equina (orange arrows) related to metastatic melanoma.
